Generally, a torque sensor to be used in an electric power steering device is disclosed in JP-A-11-248561, for example. In FIG. 9, in a housing 51 including an upper housing 51a and a lower housing 51b, an input shaft 52 and an output shaft 53 connected through a torsion bar 54 are rotatably supported by bearings 55.
A steering shaft, not shown, for example, is mounted to the upper end of the input shaft 52, and a pinion shaft 53a is integrally provided to the lower end of the output shaft 53. The pinion shaft 53a engages with a rack shaft 56. Notably, a worm wheel 57 is externally fitted into the output shaft 53. The worm wheel 57 co-axially and integrally rotates with the output shaft 53. An output shaft 59 of an electric motor is connected to the output shaft 59 through a worm 58. By transmitting a rotational force of the electric motor to the output shaft 53 through the worm 58 and the worm wheel 57, the electric motor is appropriately controlled and proper steering-assist torque can be given to the output shaft 53.
A cylinder member 60 is provided around the input shaft 52 within the upper housing 51a. A coil unit 61 is mounted on the external side of the cylinder member 60 with a predetermined amount of spacing therebetween. As shown in FIG. 10, the coil unit 61 includes a pair of electromagnetic yokes 62 and coil bobbins 63 accommodated in the electromagnetic yokes 62, respectively. Each of the electromagnetic yokes 62 is a substantially cylindrical member with an inverted C-shaped section having a radial internal part open. The electromagnetic yoke 62 includes a yoke member 62a and a yoke member 62b. The yoke member 62a has an L-shaped section and forms the circumference surface and one side surface. The yoke member 62b forms the other side surface.
As shown in FIG. 11, the coil bobbin 63 is a substantially cylindrical member with an inverted C-shaped section having a radial external part open. The coil bobbin 63 includes injection-molded flanges 63b and 63c of resin at both ends of a cylinder 63a. In the one flange 63b, a substantially parallelepiped terminal block 64 extends to the radial outside and axial outside (that is, the left side of FIG. 11). As shown in FIG. 12, the terminal block 64 has two press-fitting holes 65 and 65 from the top surface to a radially internal part. As shown in FIG. 13, two metal connection pins 66 and 66 are press-fitted and fixed into the press-fitting holes 65, respectively. Edges 67a and 67b of a coil winding 67 wound about the coil bobbin 63 are wound about the connection pins 66 and are fixed along the surface of the terminal block 64. In other words, the connection pins 66 are press-fitted and fixed into the terminal block 64. After that, the leading edge 67a of the coil winding 67 is temporarily fixed by being wound about one of the connection pins 66, and the trailing edge 67b of the coil winding 67 is temporarily fixed by winding it about the other connection pin 66. Then, the wound parts of the connection pins 66 are soaked in a solder bath, and the coil winding 67 is soldered to the connection pins 66. Here, when coats of the edges 67a and 67b of the coil winding 67 are melted by the soldering heat, the coil winding 67 and the connection pins 66 are brought into conduction. The connection pins 66 are fixed at predetermined positions of a circuit substrate 69 within a sensor case 68 of the upper housing 51a. 
However, when the connection pins 66 are press-fitted into the press-fitting holes 65 of the terminal block 64, air may be trapped by the connection pins 66 in the deepest area of the press-fitting holes 65. In this case, since the press-fitting holes 65 are not through-holes communicating with the outside, the pressure in an enclosed space s in the area deeper than the pointed ends of the connecting pins 66 increases. Especially, in order to solder the coil winding 67 to the connection pins 66, the connection pins 66 are heated. Thus, the resin of the terminal block 64 is gradually melted, and the temperature in the enclosed space s increases, causing an excessive pressure. As a result, a force from the enclosed space s within the press-fitting holes 65 in the direction indicated by the arrow in FIG. 13 acts on the connection pins 66, and the connection pins 66 may come out from the press-fitting holes 65. Thus, like the connection pins 66, the edges 67a and 67b of the coil winding 67 are pulled in the arrow direction in FIG. 13, causing an excessive stress in the vicinity of the edges of the coil winding 67. Therefore, the edges 67a and 67b of the coil winding 67 may break, and/or exposed parts of the connection pins 66 may become longer than a predetermined size.
Notably, when the press-fitting holes 65 are through-holes through the terminal block 64, the terminal block 64 projects to the axial outside of the coil bobbin 63. Thus, when the connection pins 66 are deeply pushed thereto to press-fit, the connection pins 66 may touch the yoke member 62b of the conductive electromagnetic yoke, that is, the electromagnetic yoke cover, for example, which may cause a short-circuit.
In order to attach the coil unit 61 to the housing 51a, the connection pins 66 are accommodated at a predetermined position in the axial direction of the housing 51a through a substantially-rectangular notch (corresponding to a through-hole 3 in FIG. 1) on a side wall of the housing 51a. In this case, with a low precision of the attachment to the connection pins 66, the connection pins 66 may bend during assembly due to interference with the internal wall of the housing 51a near the notch. Thus, the connection pins 66 cannot be mounted to the circuit substrate 69 precisely, which is a problem.
Accordingly, it is an object of the invention to provide a torque sensor, which can improve the attachment precision of connection pins by improving a structure for mounting the connection pins to a terminal block and securing a connection between coil winding and a circuit substrate by precisely exposing a predetermined length of the connection pins from the terminal block.